Field of the Invention
The present invention relates to heavy-duty pneumatic tires, and in particular relates to a heavy-duty pneumatic tire having a bead portion with high durability.
Description of the Related Art
Japanese Unexamined Patent Application Publication No. 11-020421 discloses a heavy-duty pneumatic tire with a reinforcing layer in a bead portion. The reinforcing layer disclosed by the publication includes a first reinforcing layer of a steel cord that extends in a U-shaped manner to surround a bead core and a second reinforcing layer of an organic fiber cord that extends in a radial direction and is located axially outward of the first reinforcing layer.
Unfortunately, when the heavy-duty pneumatic tire disclosed by the publication is used in a hot climate or a region where braking is frequently necessary, a bead rubber component proximate to the rim flange is softened by a high temperature of the bead portion and would deform so as to lean on a rim flange, and then the rubber component becomes hardened. Such a hardened rubber may cause damage such as crack and the like. Accordingly, in the conventional art, there is room for improvement of bead durability.